STOP Early Journal Content on JSTOR, Free to Anyone in the World This article is one of nearly 500,000 scholarly works digitized and made freely available to everyone in the world by JSTOR. Known as the Early Journal Content, this set of works include research articles, news, letters, and other writings published in more than 200 of the oldest leading academic journals. The works date from the mid-seventeenth to the early twentieth centuries. We encourage people to read and share the Early Journal Content openly and to tell others that this resource exists. People may post this content online or redistribute in any way for non-commercial purposes. Read more about Early Journal Content at http://about.jstor.org/participate-jstor/individuals/early- journal-content . JSTOR is a digital library of academic journals, books, and primary source objects. JSTOR helps people discover, use, and build upon a wide range of content through a powerful research and teaching platform, and preserves this content for future generations. JSTOR is part of ITHAKA, a not-for-profit organization that also includes Ithaka S+R and Portico. For more information about JSTOR, please contact firstname.lastname@example.org. THE AMERICAN NATURALIST. Vol. XXII. FEBRUARY, 1888. No. 254. ON METEORITES. 1 BY DR. HANS EEUSC'H. TI7"E know that in the organic world, besides the larger animals '* and plants, there exist immense numbers of living beings of diminutive size, from those barely visible to the unaided eye down to those which can only be discerned in powerful microscopes, and of which many thousands live in a space no larger than a drop of water. Similar is the case with the heavenly orbs revolving in the infinite space. Besides the big luminaries, numerous swarms of very small bodies are hurrying through the space in their different varying orbits. To the smallest of these — the so-called meteorites — I here wish to call your attention. There is a circumstance which imparts them with a special interest to us ; for they some- times fall to the earth, so that we are able to lay hold of them, touch them with our hands, study them chemically and microscopi- cally — in short, examine them by all the means available to us for a scientific investigation of their nature. The meteorites thus form a kind of connecting link between astronomy and mineralogy — sciences otherwise rather distant, but which in this instance are brought to mutually throw light upon each other. It is probable that, on an average, several meteorites reach the earth every day, but many falls occur at night, while others drop into the sea, are lost in deserts or in places inhabited by ignorant people. In going over the falls of meteorites which have come to our knowledge, it appears that no more than four or five cases a 1 A lecture delivered at the University of Christiania, Norway. 98 On Meteorites. year, on an average, are recorded ; and in but comparatively few instances the fallen stones are hunted up by people in order that they may become of use to science. The meteorites, therefore, owing to their variety, rank among the most precious treasures of the mineralogical museums. To illustrate the value generally attached to them, it may be mentioned that after it had become known that the meteorite found last year at Tysnses, Western Nor- way, had been acquired by the Christiania Museum, a mineralogist was dispatched by the Riks-museum, in Stockholm, Sweden, the long way across the Scandinavian Peninsula, in the hope that he might be able to pick up some fragments. A chief object of this paper is, therefore, to call the attention of the public to the meteorites, in order to prevent possible falls from being passed unheeded. The attention once aroused, it may also be possible to ferret out meteorites, the fall of which, in former times, has been kept a secret, owing to the superstition that, reduced to a powder, they might serve as a medicine for man and beast. In Norway, for instance, they were known as "thorelo" — i.e., "lo," or wadding of Thor, or thunder — the belief being that they fell during thunderstorms. Not all the stones which have been pre- served as "thorelo," however, are meteorites by any means, many of them being only common pebbles, pieces of pyrites, or some other kind of mineral. After these preliminary remarks, I shall proceed to the special subject of this paper — the meteorites and their nature — to be treated of in three separate sections, viz. : — (1) The phenomena accompanying the fall of meteorites ; (2) Their mineralogical nature, and (3) Their position as celestial bodies. The circumstances under which the fall of meteorites occur being rather similar in most instances, we may take, for an example, the fall of the Tysnses meteorite. It occurred on the 20th of Maj r , 1886, near the farm called Midt Vaage, situated on the Island of Tysnres, south of Bergen, Norway. Between eight and nine o'clock in the evening the inhabitants in a wide circle of surround- ing country were frightened by a loud report, which most of them took for a clap of thunder, the stone falling down immediately after the report. I have myself examined two grown-up persons who witnessed the meteorite coming down from the air. One was a woman working in a potato-field. She heard a loud noise, and, On Meteorites. 99 looking up into the sky, observed a black mass of clouds, from which she thought she heard a cracking sound, repeated five or six times, upon which the stone fell with a whizzing and rumbling noise a little distance off. Dust arose from the spot where it struck the ground. The woman walked up to where it fell and saw a hole in the ground, but found nothing else, as the meteorite had bounded off several yards from where it first struck. The other eye-witness ■ — a man who was a little further off — was just going home after having finished his day's work. He heard the report, and shortly after saw the stone coming down, " like a shot bird." No fiery display was noticed at the place ; but people who witnessed the phenomenon from a distance of several miles (a Norwegian mile about equals seven English miles) — as, for instance, in Bergen and in Vossevangen — observed a fire-ball darting with great speed across the sky and then exploding in the direction of Tysnses. Comparing the accounts of the direction of the fire-ball by the different observers, it appears that the meteor must have moved nearly vertically towards the earth's surface. That the fire-ball escaped the notice of those on the spot may be accounted for by its being right above their heads, as one seldom notices what occurs right over one's head. Their attention was first attracted by the report ; but as this, of course, was heard a considerable time after the explosion of the fire-ball, the fiery display had ceased long before the thundering noise could reach them, after which some time again elapsed before the stone fell. The man pointed out to me the corner of the field where he was standing at the time he heard the report; when the stone fell he had nearly reached his house. In ascertaining the distance, he found that it took him about one minute and ten seconds to walk from one place to the other. Judging from the space of time which elapsed between the report and the fall, the explosion must have taken place at a very great height above the surface of the earth. With due regard to the traveling speed of the sound and the probable celerity of the fall, the height may be estimated at twenty to thirty thousand metres ; but any certainty cannot be arrived at. The next morning a girl living close by found a big, black stone lying in the grass. She put it aside, but did not mind it any further ; and people's attention was not called to it before it was rumored that a stone had been seen falling from heaven. The fol- lowing Sunday the curious stone formed the main topic of 100 On Meteorites. conversation among the people assembled at church. An emigrant Norwegian, on a visit home from America and about to return to this country, made a bargain with the poor woman on whose land the stone was found : he was to take it away for a mere song ; and the Tysnses meteorite came thus very near going to America. On coming home, however, the woman became uneasy at the idea of selling such a God-send — direct from heaven — and she returned the money. Shortly after, the district physician, Mr. Gjestland, heard of the stone, and, realizing its great scientific value, he at once took it into his charge. It is owing to this gentleman's most obliging intervention that the stone — against a handsome remuneration, of course — was secured for the University of Christiania. This meteorjte weighs about forty pounds. Several smaller fragments were also found. The phenomena mentioned above — viz. : a fire-ball rushing along and exploding with a thunder-like report, followed by the coming down of the fragments — are those regularly observed accompanying the fall of meteorites. In some cases the velocity of the fire-ball has- been ascertained to be sixty to seventy kilometres a second. This tremendous velocity accounts for the fire phenomenon, as the atmos- phere, not being able to escape before the missile, becomes conden- sed to an enormous degree — a great quantity of heat thus being developed, according to the known physical laws. The meteorites, at one time having the temperature of space through which they were rushing — a temperature far below the freezing point — will thus become enormously heated on the outside when entering the earth's atmosphere. The pressure of the strongly-condensed atmosphere,, finally exceeding a certain limit, acts as a blasting-agency, according to a commonly-accepted opinion, and the fire-ball explodes. The fragments are still glowing for a while after the explosion, but, as a rule, they have probably become cooled off when reaching the ground. Nor is the final speed very considerable, the original velocity of the fire-ball having been diminished by the resistance of the air. When falling at full speed, the surface- of the meteorites may be supposed to be continually melting — nay, perhaps, evaporating. By the friction of the air, however, the molten substance is removed almost as fast as it is formed. In this way the "fire-tail " — which the observers in many cases affirm having seen — may be explained. In the same manner the " smoke " is formed which, on several occa- On Meteorites. 101 sions, has been observed floating in the wake of the fire-ball, after the latter has disappeared. Several people assert that such a smoke was also seen accompanying the Tysnaes meteorite. The fallen Fig. 1. The Tysnees Meteorite. stones show various signs of intense heating in the atmosphere, to which we want to direct the attention. In some cases, when stones have been taken up shortly after striking the ground, they have still been warm. In one instance it has been related that the fallen stone was at first so hot as to burn the fingers, and afterwards turned so cold that it could not be held in the hand for that reason. This may be regarded as very probable, when we consider that the heat- ing in the atmosphere only lasts a few seconds, and that its action, consequently, must be quite superficial. Space, on the other hand, has an exceedingly low temperature, and the freezing coldness of the interior of the stone will therefore soon lower the temperature of the surface. The interior of the meteoric stones, as a rule, is gray or whitish ; the exterior, on the contrary, is covered with a blackish crust, which, on examination, proves to be the stony substance, having undergone a melting process. It is difficult to tell what shape the meteorites have before entering our atmosphere, as we only gather bits and fragments after the explosion. These show the effect of the com- pressed and intensely-heated air. The edges of the fragments, originally sharp, have become rounded, and on the surface there appear deepened marks, many of which look as if the stone had 102 On Meteorites. once been soft as a dough in which the kneading-fingers had left their impressions. The air has had a consuming effect on the stone- — much in the same way as a powerful jet of sand acts on a solid body. Mr. Daubree has experimentally imitated this remarkable effect of the air. Not being able to move a solid against an aeri- form body with sufficient speed — as is the case with the meteorites — he chose to proceed in the opposite way, making air strike solid bodies with great vehemence by exploding dynamite cartridges against an iron rail. The result of the experiment showed that the gases, suddenly developed by the dynamite exploding, produced hollows even in a body of such resi sting-power as an iron rail, and the form of the impressions — in this as well as in his other experiments — corresponds exactly to those found in the meteorites. Having now considered the phenomena accompanying the fall of meteorites, we shall now direct our attention to their mineralogical nature. The meteorites maybe classed in two primary groups : stone- meteorites — to which belongs the Tyshses meteorite — and iron- meteorites, which consist chiefly of this metal. The two principal minerals composing the stone-meteorites are eustatite and olivine (or chrysolite)— both of which are also found on our globe, though rather rare — besides which these meteorites also contain grains of native iron, as an occasional sprinkling, through the mass. Examined by the microscope, they exhibit a structure which proves that origin- ally and before entering the atmosphere they were formed out of melted masses by congelation. Fouque" and Michel LeVy have produced, artificially, the structures mentioned by melting together suitable substances. It thus appears that these small heavenly bodies, in precisely the same manner as the crustof our own globe, consist of originally molten masses, having afterwards become sol- idified. In this connection, it may not be out of place to remind one of the fact that the interior of the earth consists of substances heavier than those most commonly found on the surface. The meteorite is also heavier than common stone ; and it has been conjectured (with several reasons to support this hypothesis) that the interior of the earth consists of a substance similar to that composing the meteorites. On further examining the meteorites, it is found that after having passed through the original congealing process they have undergone several changes on their way through space. In many cases it is On Meteorites. 103 mm --7S Fig. 2. Braccious structure of the Tysnees meteorite. Drawn by the author. evident that their substance has been broken into small pieces, which again have become cemented together — a structure seen with un- common distinctness in the Tysnres meteorite, as represented in the accompanying cut (Fig. 2). Not all the fragments are so large as to be seen by the unaided eye ; for in ex- amining the stone by the microscope some very small ones are also found, mostly of a round or globular form. This breaking up and putting together again seems in the case of the Tysnses meteorite to have oc- curred at least twice. The large fragments seen, in Fig. 2 are composed of smaller ones, it being a case similar to a conglomerate in which the individual roll-stones consist of conglomerate. Fig. 3 shows a portion of the Tysnses meteorite viewed in the microscope ; while Fig. 4 represents an isolated globule of olivine, greatly magnified. It contains a brownish and glassy substance, in form reminding one of the cells of plants. Similar formations, not rare in meteorites, have furnished a fanciful scientist an excuse for obstinately asserting that they actually are the remains of plants. It is to be regretted that such is not the case ; for it would undoubtedly have been interesting if in this way we had been able to lay hand on specimens of organic life from other globes. The second group of meteorites consist of native iron — as men- tioned above — with an occasional sprinkling of grains of stony minerals. Native iron occurs but rarely on this globe, as ir.on readily enters into combination with oxygen — in other words, it oxidizes, or rusts. In fact, it is so rare in nature, except in the meteorites, that any lump of iron produced by man was formerly believed to have fallen down from heaven. This was also Norden- skiold's impression when, some years ago, he found quite a quantity of native iron in Greenland. The find was at that time much talked of; but Steenstrup afterwards pointed out that the supposed meteor- ites were only big lumps of iron which had weathered out of the rock on which they were found. This rock abounded to a remark- able degree in iron. 104 On Meteorites. The iron of the meteorites, as a rule, contains more or less nickel irregularly distributed through the mass. If the polished surface of the meteoric iron be exposed to the action of some acid, there will appear peculiar linear designs, called the " Wiedmannstatten figures" (after the discoverer), the acid attacking the iron containing nickel to a less degree than the pure metal. We will now direct our attention to our third sub- ject, and consider the meteorites as celestial bod- ies. Before entering into this, it will be necessary, how- ever, to say a few words in regard to shooting-stars and comets, these being the celestial phenomena with which the meteor- ites are most nearly com- parable. To a common observer, who does not make a spe- cial study of the heavenly vault, it looks as if the shooting-stars move quite irregularly — now in this direction, noAV in another. If, however, their courses be carefully traced on an astronomical chart, it will be found that in most cases they radiate from certain points in the sky — a great many of which have already been ascertained. That the shooting-stars come from a certain point means that they are moving from that section of space towards the earth, the radiation being only the effect of the perspective as they move from the distance in the direction of the observer. The best-known swarm of shooting- stars is undoubtedly the one which appears to radiate from the constellation of the Lion, and is passed by the earth on the 1 3th of November. As on this day extremely numerous falls of stars have been observed, with a regular interval of thirty-three years, it is Fig. 3. Portion of the Tysnses meteorite, mag- nified 65 times. Globules composed of enstatlte crystals; the cementing substance in the upper globule is a brownish glass. &, grain of olivine Drawn by the author. On Meteorites. 105 evident that they belong to a swarm which, after a revolution of thirty-three years around the sun, returns to the orbit of our globe. The comets are apparently something entirely different from the shooting-stars ; for while the latter are quite small and only appear within the terrestrial atmosphere, the comets are bodies of immensely greater size,comparatively speak- ing, and moving at a very great 'J~- \ -.v.; Investigation shows, however, .M/'' distance from our little planet. Pr^6 that the orbits of both comets and shooting-stars have the same form, they being elongated c6nic sections : hence their approaching from distant dark regions of space — now close to the sun, now again retiring to an immense distance from it. In regard to one comet, it has, furthermore, been ascertained that it moves in the same orbit as the swarm of shooting-stars mentioned above. fa^Magnmedi^ u^'vrlwnlXl The exact nature of the comets au has not yet been made out with any certainty, the best-sup- ported hypothesis being that they consist of immense quan- tities of small solid bodies. The comets nearest to the sun, when tn their greatest proximity to that body, are exposed to an enor- mous heat, soon followed, as they retire, by a cooling off equally enormous. The strong influence of the sun's vicinity on the comets shows itself, among other things, in the well-known long tail, which they project on the further side from the sun, and the nature and origin of which is still rather mysterious. Neither is the true nature of the shooting-stars fully ascertained. Many of them, however, appear to be small solid bodies rushing through the air ; and there are a great many intermediate forms between the common shooting-stars and the big fire-balls which explode with a thunder- like report and emit meteoric stones. J 1 Mr. Sophus Tromholt, the author of the beautiful work, Under the Bays of Aurora Borealis, has sent me the following interesting record of a shooting-star : — " One starlight but moonless Saturday night during November or 106 On Meteorites. In the meteorites we have, as seen, at last something palpable which we tfre able to study. It will therefore be of great interest to have their connection with the shooting-stars and comets more definitely established. The study of the orbits of the meteorites, however, is rendered much more difficult than that of the shooting- stars by their comparatively much rarer and more unexpected occurrence, by the terrifying phenomena often accompanying them, and by the fact that they are seldom observed by others than ignorant people. The mode of studying the orbits of the meteor- ites must, therefore, be different from that suited to the case of the shooting-stars. > Having made a special study of the dates of the recorded falls of meteorites, I have come to the conclusidti that they, or at least some of them, may be referred to certain systems like the shooting-stars, and that in some cases periods^— suggesting a connection with a certain group of comets — may be set down with some probability. The orbit of the earth around the sun may be considered as divided into three hundred and sixty-five parts, one of which is traversed on each day of the year. That the fall of a meteorite occurs on a certain date means, then, that, the part of the earth's December, 1883, between eightand nine o'clock, as Mr. Lionses, a boob> seller in Fredrikstad, Norway, was standing in his yard looking inci- dentally up into the sky, he observed a shooting-star in the north, at a height of about 60°, moving in a curve and gradually increasing a little in size. The exact length of time he is unable to state : be had turned his eyes away, when suddenly a small, shining body fell down before his feet, not two yards off, passiug him so closely that in his fright he sprang aside. When the meteor struck the ground sparks flew in all directions, and a faint report was heard. This noise was also heard by his daughter, who at the time was in the passage leading to the yard. Shortly after — 'about a minute '—both father and daughter observed a similar meteor in the same direction, which seemed to descend behind a neighboring house. " The gentleman mentioned is uncertain as to the exact date of the observation ; but the choice seems to lie between the Saturdays, Novem- ber 3d, November 23d, and December 1st ; but as, according to the meteorological observations recorded at the Fredrikstad Station, the sky was overcast on the two former Saturdays, the fall must have taken place on December 1st, when the weather was rather clear. He has stated to me that the size of the shining body was comparable to that of a walnut, and the little fragments into which it was broken when strik- ing the ground he compared to small beads. Unfortunately, he omitted: to collect them, and later search was unavailing, as the yard had been swept several times afterwards." On Meteorites. 107 orbit designated by this date is intersected by the orbit of the meteorite. It now often happens that the earth is struck by meteorites on the same date during two or several consecutive years. This can only be explained by the earth on that date passing through a swarm of meteorites, or, rather, through a long stream taking several years in passing — if we consider that, on an average, no more than four falls of meteorites are recorded yearly. Thus, the earth was hit four times by meteorites on the 13th of December, between the years 1795 and 1813. 1 Since then the earth has not collided with any meteorites on that date. Still more remarkable than dates which, like the above, show the meteorites to go in flocks, are others from which, with a con- siderable degree of probability, we may infer a certain period. Thus, the 13th of October is a date worth mentioning, as on that day falls of meteorites occurred in 1787, 1819, 1838, 1852 and 1872. On examining the differences between these years, they will be found to be very nearly multiples of 6J — viz. : 5x6J, 3x6J and 2x6|-. These falls, consequently, seem to belong to the same flock, with a period of between six and seven years. The flock must be rather lengthened and takes a considerable time to pass, since the earth passes it so often, as is recorded in this case. If the stream be short, there is, of course, very little change of the earth being just in the point in which the orbits of the earth and the meteorites cross each other every time the stream is passing. This would only be the case if the period were exactly one or more whole years. As this, of course, occurs but very seldom, it is not to be expected that the differences between the years be exactly multiples of the periods. It may be well to quote other similar periods of meteorites. • In February, two series of falls are particularly notable, viz. : — February 19, 1785, at Witmess. " 18, 1815, at Duralla. " 16, 1876, at Indesgherry. February 19, 1796, at Tasquinha. " 18, 1824, at Irkutsk. " 16, 1883, at Alflanella. The possibility here suggests itself that the earth on February 19, 1785, met a flock of meteorites which, with a period of about thirty years, reappeared in 1815. No fall is on record from the next meeting. From the one then to follow, however — that is, from the one to take place sixty-one years from 1815 — viz., in 1876, a fall is recorded. It will be observed that the dates are receding, 1 To these falls may be added a fifth, which occurred on the Western Hemisphere, December 14, 1807. 108 On Meteorites. as the first fell on the 19th ; the second, on the 18th. The third fall, if it took place, probably occurred on the 17th; while the fourth happened on the 16th. This regular receding of the dates may be explained without difficulty as due to the precession retro- grading comparatively fast. The case of the three falls of the second column may be the same, though their period must be shorter, the difference between 1796 and 1824 being 28, and that between 1824 and 1883 being 59. We give below a list of other systems, in regard to which we remark that the figures in parentheses indicate the differences between the contiguous years: — Period — Between six and seven .years. May 9— Drake Creek 1827 " 8— Monte Milone 1846 - )Z> " 8— Dyalpur 1872~~ (26 > " 10— Estherville 1879 - ( ~> Period — Between six and seven years. May 11 — Oesel -i ' ' 12 — Bremewoerde J ' " 13— Butsura i " 14— Canelles} " 12— Kursk •> " 14— Nash County / * .1855 1861 -(6) •(13) .1874 This latter system is perhaps a double one, as in the same year two falls occur at an interval of a day. Period — Be- tween six and seven years. March 15 — St. liltienne de Lolm and Valence.. .1806 " 14-Cutro m3, ~nll " 15— Lugano 1826 ^ " 16— Rutlam 1863 )° 7 > " 14— Middlesborough 1881 (18) Period— About six years. August 10— Slobodka 1818, 23 , " 10-Iwan 1841_^J " 11— Bentham 18o9_^ J " 12— Dundrum 1865 Period — About seven years. July 3— Mixburg 1725_ (2g . " 3— Plan 1753 4— East Norton 1803 4— Crawford 1859 -(50) -(56) Period — Eight years. -Dogowola 1864 , g, -Tennasilm ....1872 June 26- " 28 — leiuiasiiiu ioii , p\ " 30— Nogoya 1880 On Meteorites. 109 ■o . , f September 5— Agen 1814 ,. ftN Penod- „ 5 _ Fehrbellin 1854 ~ 40 Eight years. 1 „ 5 _ Dandapur 1878~ (24) Period — Nine years. September 10 — Limerick 1813 . q . 10— Carlstadt 1822_| l\ " 9— Wessely 1831 In November there are several falls, suggesting periods of ten years, viz.: — November 5 — Bourbon, Vendee 1841 .,,,. 5— Nulles 1851 ' November 11 — Lowell 1846 .-.^ " 12— Trenzano 1856 November 29 — Coeenza 1820 ,„». " 30— Shalka 1850 ( > November 30— Futteb. pore 1822_, 2 q\ " 30— Myhee Caunta 1842 ( ' In the following series the five last observations correspond to a period of about twelve years : — May 19— Novgorod 1421 „„.. " 19— Schleussingen 1552_; 14 J " 18— Walringen 1698 -n08) " 17— Hampshire 1806_( 24) " 17— Perth 1830J 25 : " 17— Igast 1855 l ' The oldest date is uncertain, 131 being one less than 11x12. Suppose the period being only one-half as long as indicated above, still another date might be added — viz. : May 18, 1860, on which day a fall occurred at London. In the following system, which has a period of about twenty- three years, the dates are receding : — August 6— Dortrecht 1650 -162) " 5— Chantonnay 1812_) ' " 4 — Cirencester 1835, 47 - " 2— Pawlowka 1882~^ As a result, then, several flocks of meteorites can be pointed out,, which have a certain period, the latter being, in most cases, between six and eight years. It is noteworthy, in this connection, that the 110 On Meteorites. period of most of the comets, the return of which have been ob- served, is five or six years. The study of the dates of the different falls, therefore, not only suggests that at least a part of the meteor- ites move in orbits round the sun, but also intimates a certain rela- tion of some of them with a definite group of celestial bodies — viz. : the comets of short periods. We have thus established a new link connecting the meteorites with the comets in addition to those already known — viz. : the strong resemblance of the fire-balls to the shooting-stars, as well as the great velocity of several of the former, making it probable that they move in orbits of the same lengthened form as the comets. If called upon to define the nature of a meteorite, briefly and somewhat boldly, I should say, with Mr. Newton, the American : A meteorite is a bit of a comet. Let me add a few remarks in regard to the question whether there is anything in the structure of the meteorites which goes to confirm the views here set forth. The orbits of the meteorites being similar to those of the comets, the consequence would be, as mentioned above, that during a comparatively short, time, once in each period, when near the sun, they would be exposed to an enormous heat, succeeded by quite as enormous a cooling off in the cold parts of space. The fragmentary (chondrite) structure, so general in the stony meteorites, is perhaps to be explained in this way. On the earth the annual and daily heating and cooling produces, as we all well know, the weathering or general crumbling of the earth's crust, the formation of stones, gravel, sand and dust. There is a difference in regard to the meteorites, in so far as they are not covered with water or surrounded by an atmosphere, by which agencies the weathering of our earth is brought about; but, on the other hand, the difference between the heat and the cold, owing to this very want, and especially to the form of the orbit, must be enormously greater on the meteorites; for while the differences of temperature on the earth rarely rise to 50° C, the changes which take place on the meteorites must be estimated at 1,000° C, or more. It may not, then, be unreasonably supposed that the fragmentary struc- ture so common in the stony meteorites is due to the changes of temperature they have undergone. How the fragments may have become rounded off by being ground against each other or in some other way, may easily be conceived, as there are plenty of instances in regard to comets, in which movements in their mass have been observed. Theoretically, the study of the Tysnses mete- On Meteorites. Ill orite is interesting, not only for the fact that it clearly shows the chondrite structure to be of a fragmentary nature, but especially because it affords proof of the process having been repeated — a cir- cumstance not at all surprising in a celestial body which, in its wanderings through space, has repeatedly approached close to the sun. In addition to the above, it should also be remembered that the gases— carbonic acid, carbonic oxide and hydrogen — which have been successfully extracted from meteorites, are said to give the same spectroscopical lines as the comets when approaching the sun. The above explanation of the different peculiarities in the struc- ture of the meteorites is advanced here, of course, chiefly to instigate further investigation. As here propounded, it does away with all moments which may not be reasonably admitted in regard to the orbits of these celestial bodies, thus, for instance, making unneces- sary any recourse to volcanic or other processes supposed to have taken place on distant globes once large, but long since exploded. In support of this latter theory — viz.: that the meteorites have originally belonged to globes of considerable dimensions — it has been argued that the formation of so large crystals as are found in some iron meteorites can only have taken place on a celestial bodv of respectable size. The correctness of this inference may well be doubted. It is true that on our earth — which, in this connection, may be regarded a big globe — some minerals form large crystals during a slow growth ; but it cannot be inferred from this fact that large crystals cannot appear on a very small one. The mere circum- stance that in the latter the force of gravity is practically nil makes matters there stand quite differently from what they are on a great celestial body. It may be supposed that as the force of gravity plays only an insignificant part, those other forces which produce the arrangement of the molecules in the crystals are allowed to have their play much more freely than under other circumstances. The smallness of the meteoric masses may perhaps also account for their easy crumbling and the dislocation of the fragments. The minerals of the meteorites, which on our globe appear to belong to the com- paratively heavy substances, may in a certain sense be said to weigh nothing as long as they form part of a celestial body perhaps not a yard in diameter. Among other things, it may also be supposed that the electric forces called into activity by the violent changes of temperature 112 On Meteorites. play a much greater rdle than we might be apt to imagine, judging from the processes which take place on our earth. Finally, I may mention that in some meteorites there is found evidence of their having been exposed to an enormous heat after their original formation. Several meteorites — particularly one from Steelldal, Sweden, which I have examined myself — show traces of an inner melting which must have taken place somewhere in space before entering our atmosphere, and which has nothing to do with the ignition of their surface in the latter and the molten crust Fig. 5. The Steelldal meteorite viewed in microscope. ¥ by the author. Drawn thus produced. The appended cut (Fig. 5) shows a portion of the Staelldal meteorite sixty-five times magnified. The black parts are iron ; the light ones are pieces of unmolten substance swimming in a brownish glass, the chemical composition of which is like that of the unmolten substance. It will thus be seen that in the structure of some meteorites we have a direct proof of their orbits being of the same striking form as those of the comets, which alternately approach close to the sun and then again recede far from it.